The eukaryotic cell is highly organized, containing organelles that efficiently divide its many tasks. Membranes separate the organelles from one another, sustaining each in a unique chemical environment. In addition, proteinaceous channels exist in the membranes that recognize and transfer certain molecules between the cytosol and a specific organelle. Among the least understood of these channels are those that import proteins bound for certain organelles. The proposed research will use a combination of biochemistry and electrophysiology to identify and characterize the mechanism of proteins composing the outer membrane channel of a model organelle, the chloroplast. The long term objectives of the research are twofold: first, to understand on a molecular level how these channels form a semipermeable barrier between the organelle, and second, to determine how specific recognition of a signal sequence opens a channel.